In International Patent Application WO 2004/035515 a method is described for the manufacture of a mixture of a dicarboxylic acid and a diol that is suitable for the manufacture of polyesters. For this purpose the dicarboxylic acid is suspended in water, decolorized by hydrogenation and the aqueous suspension obtained thereby reacts with the diol forming a hydroxyalkyl ester; the hydroxyalkyl ester is subsequently converted to the polyester. It is however disadvantageous that the esterification of the dicarboxylic acid ester, for example the terephthalate proves to be difficult and as a result necessitates special reaction conditions.
Special reaction conditions are even more necessary if for example terephthalic acid or another dicarboxylic acid is present in an acetic acid or monocarboxylic acid-water mixture, since under these reaction conditions the esterification with a diol occurs according to another mechanism and splitting of the ester formed is strongly favored.
Methods are know already from the International Patent Applications WO 2004/052820, WO 2004/052821 and WO 2004/052822 for the manufacture of polyethylene terephthalates in which the hydrogenation is carried out in an acetic acid medium. From International Patent Application WO 2004/063139 a method is known for manufacture of high purity polyethylene terephthalates in acetic acid medium without hydrogenation. Admittedly there the use of crude acetic acid polyethylene terephthalates and intermediate products for the further manufacture of polyesters is not described.